Abstract Background Viral Hepatitis B is of a major public health concern globally, especially in developing countries. Expectant mothers’ knowledge of Mother-To-Child Transmission (MTCT) of the disease is significant in preventing the spread from an infected mother to her child. This study sought to assess the expectant mothers’ knowledge of Mother-To-Child Transmission of viral hepatitis B in the Wa Municipality and Lawra District of Upper West Region, Ghana. Methods A descriptive cross-sectional study with a multi-stage sampling technique was employed to select a total of 450 study respondents (expectant mothers), and a semi-structured questionnaire was used for the data collection. Respondents were interviewed using face-to-face interview technique. Results Majority (54.0%) of the respondents were aged between 25 and 35 years and the results were similar in both districts. Overall, 62.4% (281/450) of the respondents had at least Junior High level education, and 76.2% (343/450) were multigravida. Educational levels among respondents in the two areas were above 50.0% and considered relatively high. Respondents’ general knowledge of hepatitis B infection and disease was 46.0% (208/450). However, there was a slight difference between the two districts (40.1% in Lawra District and 51.6% in Wa Municipality). The overall knowledge level on MTCT of viral hepatitis B among the respondents was 34.7% (156/450): the Wa Municipality recorded higher knowledge (43.3%) compared to 24.8% in Lawra District. Conclusion The knowledge level of the expectant mothers on MTCT of viral hepatitis B is relatively low in Upper West Region, Ghana. Majority of the respondents had some form of formal education. The age, marital status, education, occupation, gravity and family setup were found to be associated with knowledge of Hepatitis B infection and MTCT. Thus, there is urgent need to intensify efforts of health staff to educate expectant mothers. In addition, home education and outreach activities should be intensified on HBV infection as well as MTCT. Consequently, planning, implementation and execution of preventive activities, especially in the antenatal clinics should critically consider the social and demographic variations of mothers.